This invention relates to telecommunications apparatus and methods. More particularly, this invention relates to apparatus and methods for transmitting signals (specifically signals with information or a data content) in multiple different formats.
The formats may simply be alternative technical representations of the same information; for example, different graphics formats. Alternatively, each format may be in a different medium; for example, image, text and audio formats. Further, the formats may represent something of the same information content but using different volumes of data; for example, a text file and a facsimile image made up of the characters of the text represent different formats for the same text information.
In conventional telecommunications, a given user is associated with a given telecommunications terminal (e.g. a conventional telephone, or a computer with a modem, or a facsimile unit). However, more recently, users have become mobile. In addition to mobile telephones (for example digital cellular telephones such as those conforming to the GSM standard) other types of portable terminal include pagers (either tone pagers or message pagers which can receive short textual messages and display them); so called xe2x80x9cpersonal digital assistantsxe2x80x9d (PDA""s) and portable facsimile or computer units adapted to communicate via cellular networks using dedicated modems.
At the same time, the volume of different types of formats within which information can be transmitted is increasing, and new, so called xe2x80x9cmulti-mediaxe2x80x9d formats, consisting of single sets of information presented in multiple media (such as for example image, text and audio files) are entering use.
The telecommunications channels through which information is delivered comprise channels of varying bandwidth, including optical fibre links; coaxial copper links; conventional subscriber telephone lines; infra-red local area networks; and radio transmission channels. Of these, radio frequency channels are used for mobile communications. However, radio frequency channels generally have available the lowest bandwidth due to demands on the RF spectrum and to the channel conditions within the RF spectrum.
It is becoming increasingly common for large organisations to provide local area networks within a building or group of buildings, at which a number of different terminals of different types are provided. For example, powerful workstations such as Sun (TM) workstations, may be connected on the same network as less powerful personal computers, advanced telephones, and conventional telephones. Depending on the access conditions, different users may have access to a number of different terminals within such a network, each with different capabilities of receiving information in different formats.
Various prior proposals have been made to attempt to meet the needs of mobile users dealing with data in different formats. For example, our earlier application WO 95/30317 (U.S. application Ser. No. 08/732,321 filed Jan. 22, 1997)describes an xe2x80x9cagent basedxe2x80x9d telecommunications system in which the position of a mobile user is tracked and, when he is in a cell which permits only low bandwidth information transfer, the incoming signal is either cached for later retrieval or the link is down graded (e.g. from video to voice).
Similarly, the article xe2x80x9cThe network with smarts, new agentxe2x80x94based WANs presage the future of connected computingxe2x80x9d, Andy Reinhardt, BYTE October 1994, pages 51-64, describes the proposed IBM xe2x80x98Intelligent Communicationsxe2x80x99 service (apparently intended to be marketed in late 1995) which allows a user to set up a routing profile so that when a fax is received for the user it may be converted to text using optical character recognition, and then converted to speech and read into a voice mailbox.
Our earlier application WO 95/15635 (U.S. application Ser. No. 08/652,433 filed Nov. 1, 1996), describes an agent based telecommunications system for use in a multiple services network.
Our earlier application WO 96/25012 (U.S. application Ser. No. 08/875,890, filed Oct. 14, 1997) describes a multimedia telecommunications system employing reconfigurable agents. Aspects of this document are incorporated by reference herein.
Our earlier international application WO 94/28683 (U.S. application Ser. No. 08/233,631 filed Apr. 26, 1994, now U.S. Pat. No. 5,802,502 issued Sep. 1, 1998) includes an embodiment in which, within a single network, parts of the network set up a service by obtaining prices from other parts of the network. Thus, when a user desires to transmit through the network, he polls a first part of the network, and which polls further downstream parts of the network, and so on, each part of the network then transmitting back a price. Whilst this arrangement is suitable in many applications, as networks grow in size the amount of signalling generated within the network may be substantial.
U.S. Pat. No. 5,446,553 (Motorola) discloses a fax messaging system in which, when a user is unavailable, incoming messages are stored for later access.
According to the invention we provide a telecommunications system which routes messages therethrough, in which bidding takes place in two stages; a first stage in which an estimated bid is made prior to derivation of the route, and, if accepted, a second stage in which the route is set up by a further bidding process. This has the advantage of reducing the number of bidding (and therefore signalling) entities at any time whilst maintaining a reasonable response time in setting up the route.
Furthermore, in a preferred embodiment, multiple passes may be employed corresponding to successive layers of a hierarchical organisation of bidding entities, those entities in the middle layers acting as resource suppliers to entities in layers above them and as resource purchasers to entities in layers below them. This enables further increases in the size of the network without vastly increasing the volume of signalling traffic across the network, particularly if (as preferred) the entities in each layer are geographically distributed.
For example, the arrangement adopted may consist of an entity storing data relating to each customer and arranged to decide whether or not to accept a service on behalf of that customer; a number of service offering entities each of which is arranged to offer a service at a price in the first pass; and, for each service offering entity, a number of resource entities each corresponding to an available network resource (such as a signal format converter or a signal path).
In the preferred embodiment the present invention provides a telecommunication system in which, as in some of the above proposals, a user is tracked, and the identity of a terminal which he may at any time be using is stored. Further, the present invention provides, in one aspect, storage of the capabilities (i.e. formats in which signals can be accepted and/or output) of terminal equipment in the vicinity of the user.
Therefore, rather than attempting (unsuccessfully) to deliver a high bandwidth signal to a low bandwidth mobile terminal, the system of the present invention directs the signal to a nearby terminal which can support a better representation of the signal. The nearby terminal may accent and output the signal in its original form, or the network may convert the signal to a different format which can be accepted by the nearby terminal.
Thus, according to this embodiment of the invention, the network supports a number of different signal format conversions, and is able to choose between the different terminals and associated different format capacities in the neighbourhood of a given mobile user.
It may at this point be mentioned that in so-called xe2x80x98Computer-Telephony Integrationxe2x80x99 (CTI), it has been proposed to group a computer and a telephone on the same desktop together; to note when a particular user logs onto the computer, and to route all that user""s telephone calls to the telephone with which the computer shares a desktop, thus effectively tying together a particular telephone and a particular computer in a pair.
This differs fundamentally from the above embodiment, in which the nature of each terminal in an area is stored and a given terminal is selected depending on the format of the input signal.
For this aspect of the invention to be useful, the signal must not be delivered to a terminal which is too distant to the user. Accordingly, the system must maintain accurate information of a large number of terminals, so as to establish a xe2x80x9ccommunications neighbourhoodxe2x80x9d around any position at which a mobile user might be located. Thus, fairly frequent position update messages tracking the position of the user, and terminal update messages tracking changes to the capabilities of the terminals may take place.
In order to avoid the possibility of such messages swamping the signalling capacity of the network, in a preferred embodiment the present invention provides for a hierarchical arrangement of location data storage, with distributed local databases (e.g. one per LAN, or one per building, or one per cell, microcell or picocell) storing details of the terminals provided therein and the users located close by, and at least one higher layer of databases each covering an area corresponding to plurality of the local databases and containing, for each user within the wider area, a pointer to the local database within which the user is located.
Thus, when a user changes position, the position change signal need be transmitted only as far as the local database within the area in which he moves or, if he changes from the area of one local database to another, to the new local database and to the next database up in the hierarchy containing both local databases. Likewise, changes in terminal equipment need only be signalled within the area of a local database or to the layer above.
Other aspects and embodiments are described below, with advantages which will be apparent hereafter.